125,000 years of ocean warming in 50 years: What does it mean for sea levels?
The last time the Earth's oceans were this warm, the water level was two to three stories higher than it is today, according to a new research paper.
A woman looks at a roller coaster sitting in the ocean after hurricane Sandy, in Seaside Heights, N.J., Nov. 28, 2012.
Analysis of past warming events suggests that global sea levels could rise 20 to 30 feet above today's levels, scientists say.
Andrew Burton/Reuters
What do Boston, Miami, and New Orleans have in common? All three may be almost completely underwater someday, if the results of a recent research paper are accurate.
The last time surface ocean temperatures were as warm as they are today, sea levels were , according to findings published Friday in the journal Science. Using data from a wide range of locations, the study was able to measure regional temperature changes聽and concluded that recent models may be underestimating warming trends.
Earth鈥檚 climate features cyclical ice ages, when temperatures drop and ice sheets spread, causing ocean levels to fall. We currently enjoy the mild climate of what鈥檚 known as an 鈥渋nterglacial period,鈥� when warmer temperatures melt ice, raising the seas. To better understand how our climate may develop in the future, experts consider the last interglacial period, 129,000 years ago, to be of great importance.
Getting a snapshot of what was going on so long ago isn鈥檛 easy, but scientists have a few tricks up their sleeves, such as measuring the makeup of ancient ice cores. This study used the composition of plankton shells (which depends on surface temperature) found in ocean sediments from 83 sites worldwide to compare our current interglacial period to the last one.
While it took a 125,000 years to raise ocean temperatures by 0.9 degrees F., as The Los Angeles Times explained, current conditions have seen similar warming in less than 50, the paper found.
One degree may not seem like much in terms of the daily weather forecast, but it can have an outsized impact on sea levels. 鈥淭he last interglacial is extremely interesting because it鈥檚 the last time period in recent Earth history when global temperatures were a little bit higher and global sea level was about 6 to 9 meters (20 to 30 feet) higher,鈥� lead author Jeremy Hoffman told The LA Times.
鈥淭his tells us that the to just a little bit of warming,鈥� Rob DeConto, a climate scientist at the University of Massachusetts, Amherst, who was not involved in the research, explained to The Guardian. 鈥淭hat鈥檚 a really powerful message.鈥�
It鈥檚 also a familiar lesson to anyone who鈥檚 noticed how much faster ice cubes melt in a room-temperature drink than in a cold one.
have predicted similar 20-foot ocean level rises, but this study paints a more nuanced picture of the past climate by drawing on data from dozens of locations, rather than just a few. Researchers concluded that climate change during the last interglacial period was uneven, with different regions warming, or even cooling, at different rates, something that mirrors what聽we鈥檙e seeing today.
The researchers also found that current climate models predicted less warming, on average, during the last interglacial period than the amount they actually measured, which has alarming consequences for future trends.
鈥淭his refined picture really clearly identifies that the modelling experiments do not create enough warming during the last interglacial,鈥� Dr. Hoffman told The Guardian.聽鈥淲e think there might be some process missing that we鈥檙e just not capturing,鈥� he continued. 鈥淚f we鈥檙e missing something from this period of the Earth鈥檚 history, what might we be missing from future projections?鈥�
Global sea rise is already underway: some . The United Nations expects another . If the current temperature has the same melting effect it did last time, 30 feet of rising waters worldwide 鈥� almost twice the population of the United States.
If there is a silver lining, it鈥檚 the long timescale: no risk of a ". 鈥淭he good news is that with luck it will continue to rise slowly, so that we have time to adapt, but the bad news is that eventually all our present coastal city locations will be inundated,鈥� University of Exeter climate scientist Andrew Watson told The Guardian.
But only if we use the time well. 鈥淲e are rapidly approaching ocean conditions that haven鈥檛 been really seen on this planet for over 120,000 years,鈥� Hoffman told The LA Times. 鈥淭hat鈥檚 a very relevant thing as we head into the next couple decades, and we start making policy decisions to turn this train around.鈥�
You can check out how your city would handle 20 feet of water with nonprofit news organization .